1. Field of the Invention
The present invention relates to a power-conserving type fluorescent lamp. The present invention also relates to a power converter which may be coupled to a fluorescent lamp or a fluorescent lamp illumination device so as to allow the fluorescent lamp to be lit with a relatively small amount of power.
2. Description of the Related Art
In recent years, from the perspective of global warming and maximization of utility of energy resources, great efforts have been made to realize energy conservation in various fields. In the field of illumination devices incorporating fluorescent lamps, attempts have been made to reduce power consumption by employing inverter electronic circuitry for lighting circuits used in illumination devices. However, illumination devices incorporating a magnetic ballast (choke coil) are still in wide use because they are inexpensive. In particular, rapid-start type fluorescent lamp illumination devices incorporating a magnetic ballast are frequently used in public facilities such as schools or gymnasiums, offices, warehouses, or factories. However, since such illumination devices do not have a light regulation function, there is a problem in that it is impossible to control power consumption by regulating the brightness according to each particular need.
Therefore, there has been a need for a fluorescent lamp which can be mounted in an illumination device incorporating a magnetic ballast, and yet is capable of being lit with a relatively low power consumption.
A rapid-start type fluorescent lamp is a type of fluorescent lamp in which a preheating current always flows through a filament of the lamp while the illumination device is on. A rapid-start type fluorescent lamp utilizes a preheating current which flows through the filament of the fluorescent lamp so as to lower a discharge initiation voltage of the lamp, so that the lamp can be immediately activated after being turned on. As a result, glow starters or the like are not employed in such illumination devices.
In a rapid-start type fluorescent lamp, electrode pins of the fluorescent lamp are coupled to both a preheating circuit and a lighting circuit which supplies a lamp current. Therefore, any resistors and/or capacitors which are inserted between the electrode pins and the filament for regulating the lamp current may act to lower the preheating current as well as the lamp current. As a result, it becomes difficult to obtain the level of preheating required for activation, preventing the fluorescent lamp from being activated.
A technique for lighting a rapid-start type fluorescent lamp with a relatively small amount of power is disclosed in U.S. Pat. No. 4,435,670. According to this conventional technique, after the fluorescent lamp is activated, the heat generated in the fluorescent lamp is detected with a thermistor, upon which the preheating circuit of the fluorescent lamp is isolated, and a lamp current is routed so as to be supplied to fluorescent lamp via a capacitor. As a result, the lamp current while the fluorescent lamp is lit is reduced by the use of the capacitor. However, this conventional technique has a problem in that once the fluorescent lamp is turned off, the fluorescent lamp cannot be lit if turned on immediately after being turned off. This is because it takes some time for the temperature of the lamp to be sufficiently lowered after the fluorescent lamp is turned off; during this period, the preheating circuit of the lamp remains isolated, preventing the lamp from being lit.
A technique for lighting a rapid-start type fluorescent lamp with a relatively low power consumption, which does not involve interrupting a preheating current, is known from U.S. Pat. Nos. 3,954,316 and 4,163,176 (hereinafter referred to as the xe2x80x9cSylvania method).
FIG. 26 is a diagram illustrating the principles by which a fluorescent lamp can be lit with a relatively low power consumption according to the Sylvania method. As shown in FIG. 26, according to the Sylvania method, a preheating power source 201 and a filament 202 are coupled via a transformer 203. A preheating current and a lamp current are separated, so that only the lamp current is reduced by a current regulation capacitor 206. As a result, the fluorescent lamp can be lit with a relatively low power consumption.
According to the Sylvania method, a large amount of copper and ion materials are used for the transformer 203, resulting in a large mass and volume thereof. In the case where a fluorescent lamp is mounted in a conventional illumination device, it is necessary to satisfy an inter-electrode distance (or the xe2x80x9cfull lengthxe2x80x9d of the lamp) defined under the relevant standards. Incorporating such a large-volume transformer in a fluorescent lamp is not practical because the length of an emission tube will be significantly sacrificed. Moreover, according to the Sylvania method, the preheating current during the ON-period of the fluorescent lamp cannot be reduced. Thus, although capable of realizing a fluorescent lamp which requires a relatively low power consumption, the Sylvania method has problems associated with resource and energy conservation.
The lighting circuit for a rapid-start type fluorescent lamp incorporating a magnetic ballast can be generally classified into resonance type lighting circuits and lead-peak type lighting circuits. There is a problem in that while the aforementioned Sylvania method can be used for the lead-peak type lighting circuit, it cannot not be used for the resonance type lighting circuit.
In one aspect of the invention, there is provided a fluorescent lamp including: an emission tube for generating a luminous flux; a first filament provided at one end of the emission tube; a second filament provided at another end of the emission tube; first current regulation means having a first impedance: a first electrode pin coupled to one end of the first filament via the first current regulation means; a first switch coupled in parallel to the first current regulation means; a second switch; a second electrode pin coupled to another end of the first filament via the second switch; and a control circuit for controlling the first switch and the second switch so as to be opened or closed, wherein the control circuit closes the first switch and the second switch before the fluorescent lamp is lit and during a nominal lighting period after the fluorescent lamp is lit, and opens the first switch and the second switch during a power conservation lighting period following the nominal lighting period.
In one embodiment of the invention, the control circuit opens the first switch and the second switch after a predetermined period has elapsed since a current flows between the first electrode pin and the second electrode pin.
In another embodiment of the invention, the control circuit includes luminous flux detection means for detecting the luminous flux; and the control circuit opens the first switch and the second switch when the luminous flux detected by the luminous flux detection means exceeds a predetermined value.
In still another embodiment of the invention, the first current regulation means includes at least one element selected from the group consisting of a capacitor, a resistor, a coil and a thyristor.
In still another embodiment of the invention, the fluorescent lamp further includes display means for displaying whether or not the fluorescent lamp is operating in a power-conservation lighting mode.
In still another embodiment of the invention, the fluorescent lamp further includes second current regulation means having a second impedance, and a third switch coupled in parallel to the second current regulation means; the control circuit is coupled to the first electrode pin via the second current regulation means; and the control circuit opens the third switch during the power conservation lighting period.
Alternatively, a fluorescent lamp according to the present invention includes: an emission tube for generating a luminous flux; a first filament provided at one end of the emission tube; a second filament provided at another end of the emission tube; first current regulation means having a first impedance; a first electrode pin coupled to one end of the first filament via the first current regulation means; a first switch coupled in parallel to the first current regulation means; a second switch; a second electrode pin coupled to another end of the first filament via the second switch; and a control circuit for controlling the first switch and the second switch so as to be opened or closed, wherein the control circuit closes the first switch and the second switch before the fluorescent lamp is lit and during a nominal lighting period after the fluorescent lamp is lit, and is adapted so as to be capable of switching the first switch and the second switch so as to be both opened or closed during a power conservation lighting period following the nominal lighting period.
In another aspect of the present invention, there is provided a power converter which includes: a first electrode pin and a second electrode pin which are adapted so as to be capable of being electrically connected to two electrical contacts of a socket of a rapid-start type fluorescent lamp illumination device; a first electrical contact and a second electrical contact which are adapted so as to be capable of being electrically connected to two electrode pins of a filament of a fluorescent lamp to be mounted to the fluorescent lamp illumination device; current regulation means having an impedance and coupled between the first electrode pin and the first electrical contact; a first switch coupled in parallel to the current regulation means; a second switch coupled between the second electrode pin and the second electrical contact; and a control circuit for controlling the first switch and the second switch so as to be opened or closed, wherein the control circuit closes the first switch and the second switch before the fluorescent lamp is lit and during a nominal lighting period after the fluorescent lamp is lit, and opens the first switch and the second switch during a power conservation lighting period following the nominal lighting period.
Alternatively, a power converter according to the present invention includes: a first input terminal and a second input terminal which are adapted so as to be capable of being electrically connected to two wires extending from a lighting circuit to a socket in a rapid-start type fluorescent lamp illumination device for lighting a fluorescent lamp; a first output terminal and a second output terminal which are adapted so as to be capable of being electrically connected to two wires in electrical connection with electrical contacts of the socket; current regulation means having an impedance and coupled between the first input terminal and the first output terminal; a first switch coupled in parallel to the current regulation means; a second switch coupled between the second input terminal and the second output terminal; and a control circuit for controlling the first switch and the second switch so as to be opened or closed, wherein the control circuit closes the first switch and the second switch before the fluorescent lamp is lit and during a nominal lighting period after the fluorescent lamp is lit, and opens the first switch and the second switch during a power conservation lighting period following the nominal lighting period.
Thus, the invention described herein makes possible the advantages of (1) providing a power-conserving type fluorescent lamp to be used in conjunction with an illumination device incorporating a lead-peak type lighting circuit, such that a reduction in the power consumption can be achieved by simply replacing a conventional fluorescent lamp with the power-conserving type fluorescent lamp according to the present invention; (2) providing a power-conserving type fluorescent lamp which can be adapted to both a resonance type lighting circuit and a lead-peak type lighting circuit, such that a reduction in the power consumption can be achieved by simply replacing a conventional fluorescent lamp with the power-conserving type fluorescent lamp according to the present invention; and (3) providing a power converter which can be easily mounted to an illumination device or a conventional fluorescent lamp incorporating a rapid-start type ballast (a lead-peak type lighting circuit or a resonance type lighting circuit), whereby the power consumption of the fluorescent lamp can be reduced.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.